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Topic: The Origin of Water on Earth (Read 2150 times)

I've been looking for answers to the origin of water on Earth, and all I can find are theories about it coming from comets or volcanic out gassing. Does anyone have any other ideas, because neither of these make sense to me. (Though volcanic out gassing is much more plausible than comets.)

Yeah, but the reason I distrust collision theories is because the volume of water on earth is an estimated 1.4 billion cubic kilometers. This would either require the collision of nearly 6 million standard size comets, or a single comet 3000 kilometers in diameter (or the distance from San Diego, CA to Jacksonville, FL). If they were standard comets, we would have to had seen one collision every 800 years over the last 4 billion years. Each collision would be an extinction level event. It seems we'd have record of this, no? It just seems like there are a lot of holes (craters, haha) in the collision theory....

This is a good question. The amount of water on earth is quite large, but it doesn't seem to be hugely out of line. There are other bodies in the solar system with comparable or greater amounts of water: Europa, Encleadus and maybe some Kupier Belt objects. Water could have come from comets, or naturally formed from clouds of hydrogen and oxygen during the early stages of the solar system's development, but there is another possibility: Life.

Water can be produced from organic reactions involving Hydrogen Sulfide and Carbon Dioxide. Both of which should have been abundant in the young Earth's atmosphere.

Water is a simple molecule composed of two of the most common elements (literally the top one). The question isn't why is there so much water, but why is it so rare elsewhere.

Second, the comet thing. When the solar system formed there was a hell oif a lot more comets as the planets where forming. They devoured them to build their mass up like vaccums long before life could begin to form.

I've heard theories from sceintists that beleive both mars and venus possessed oceans till natural disasters destroyed them. Mars seems to have lost too much atmosphere to keep liquid oceans and Venus' run away green house event baked the water back to it's coponets. The hydrogen escaped the planet and the oxygen refused into new elements.

Water is a simple molecule composed of two of the most common elements (literally the top one). The question isn't why is there so much water, but why is it so rare elsewhere.

Second, the comet thing. When the solar system formed there was a hell oif a lot more comets as the planets where forming. They devoured them to build their mass up like vaccums long before life could begin to form.

I've heard theories from sceintists that beleive both mars and venus possessed oceans till natural disasters destroyed them. Mars seems to have lost too much atmosphere to keep liquid oceans and Venus' run away green house event baked the water back to it's coponets. The hydrogen escaped the planet and the oxygen refused into new elements.

From what I've read, water is abundant in ice form in the outer parts of the galaxy. The orbits of comets allows them to enter the inner galaxy, and this is why they think (at least some) water came from comets.

How did the moon come to orbit Earth? Gravity pulled it in. Specifically, a planet smaller than Earth collided at an oblique angle in a monstrous collision. The collision sprayed debris out into space. Some of the debris fell back to Earth. While other pieces orbited the planet. Over time, the orbiting debris coalesced into ever bigger chunks until there was only one chunk remaining. This explains why the Earth and the Moon have the same elemental balance.

How did anything get to Earth? Gravity pulled it in.

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Ganymede and Europa: Is that confirmed? Last I checked, the 'water' there was simply suspected and was mostly ice. How have they confirmed it is, in fact, H2O?

First of all, ice is H20, it's not in some chemical class of its own just because it's too cold out there to be liquid. Europa seems to be mainly composed of ice, with a liquid center, similar to how the Earth has a solid crust and a liquid center (generalizing here). Ganymede I am not so familiar with. Mars, though, also has water - a fair bit of it, too, though it's all frozen now. Again, whether the water is frozen or not is irrelevant to the question of how it got onto a planetoid in the first place.

Also, as someone pointed out, even planets with no water can gain water through chemical reactions of hydrogen- and oxygen-containing compounds (usually an acid and an oxide).

Ganymede and Europa: Is that confirmed? Last I checked, the 'water' there was simply suspected and was mostly ice. How have they confirmed it is, in fact, H2O?

First of all, ice is H20, it's not in some chemical class of its own just because it's too cold out there to be liquid. Europa seems to be mainly composed of ice, with a liquid center, similar to how the Earth has a solid crust and a liquid center (generalizing here). Ganymede I am not so familiar with. Mars, though, also has water - a fair bit of it, too, though it's all frozen now. Again, whether the water is frozen or not is irrelevant to the question of how it got onto a planetoid in the first place.

Also, as someone pointed out, even planets with no water can gain water through chemical reactions of hydrogen- and oxygen-containing compounds (usually an acid and an oxide).

My statement was simply composed wrong. I wasn't saying that ice doesn't count as water. I was trying to ask how they know it's ice/water on those planets/moons.